1. The field of art to which the invention pertains comprises the art of fluid handling including apparatus for selfcompensated fluid pressure control.
2. A common need that frequently arises in both industry and science is the requirement to supply fluid for a variety of purposes at carefully controlled predetermined values of pressure. One such purpose may be for the calibration of instruments or control devices to ensure accuracy of their operation while another may be for direct external pressure monitoring. For these situations and others, various programmable pressure control apparatuses are commercially available and/or are known in the art as exemplified by prior art U.S. Pat. No. 3,113,582; 3,482,588; 3,315,250; and 3,598,138.
While apparatus of the prior art has undoubtedly functioned well in meeting the variety of requirements for which they have been used they frequently are characterized as being analog in nature and of only moderate accuracy subject to such other deficiencies as calibration shift or the like. Despite recognition of the foregoing limitation, it has not heretofore been known how to construct a highly accurate BCD operated pressure control system less prone to the calibration shift and other inaccuracies of the prior art.